WIP 1.21.5 support

[Seanspt]

working but with errors.

1. PartialReadError: Read error for undefined : Unexpected buffer end while reading VarInt.
2. Can see bot messages in background logs, but no messages show in game chat box.

[GetNameSniped]

could the chat issue be related to this?:
https://www.minecraft.net/en-us/article/minecraft-java-edition-1-21-5

The serverbound chat and chat_command_signed packets now contain a checksum byte along with the "last seen" update

This is a simple hash of the "last seen" signatures which should be reconstructed by the server, allowing quicker detection of desynchronized state
This can be passed as 0 to disable the check, for compatibility with protocol translation

[Seanspt]

The bot messages works in game started with official launcher. But not work in prism launcher. Don't know why.